The present invention relates generally to connectors for terminating coaxial cable. More particularly, the present invention relates to a coaxial cable connector having improved radio frequency integrity (RFI) sealing.
It has long been known to use coaxial cable to carry communication signals from an external source to various electronic devices such as televisions, radios and the like. Conventional coaxial cables typically include a center conductor surrounded by an insulator. A conductive foil is disposed over the insulator and a braided conductive shield surrounds the foil covered insulator. An outer insulative jacket surrounds the shield.
It is also well known to use connectors to terminate coaxial cable so as to connect the cable to the various electronic devices. Prior art coaxial connectors generally include a connector body having an annular collar for accommodating the coaxial cable, an annular nut rotatably coupled to the collar for providing mechanical attachment of the connector to an external device and an annular post interposed between the collar and the nut. A resilient sealing O-ring may also be positioned between the collar and the nut at the rotatable juncture thereof to provide a water resistant seal thereat. The collar includes a cable receiving end for insertably receiving an inserted coaxial cable and, at the opposite end of the connector body, the nut includes an internally threaded end extent permitting screw threaded attachment of the body to an external device.
This type of coaxial connector further typically includes a locking sleeve to secure the cable within the body of the coaxial connector. The locking sleeve, which is typically formed of a resilient plastic, is securable to the connector body to secure the coaxial connector thereto. In this regard, the connector body typically includes some form of structure to cooperatively engage the locking sleeve. Such structure may include one or more recesses or detents formed on an inner annular surface of the connector body, which engages cooperating structure formed on an outer surface of the sleeve. A coaxial cable connector of this type is shown and described in commonly owned U.S. Pat. No. 6,530,807.
In order to prepare the coaxial cable for termination, the outer jacket is stripped back exposing an extent of the braided conductive shield which is folded back over the jacket. A portion of the insulator covered by the conductive foil extends outwardly from the jacket and an extent of the center conductor extends outwardly from within the insulator.
Upon assembly, a coaxial cable is inserted into the cable receiving end of the connector body, wherein the annular post is forced between the foil covered insulator and the conductive shield of the cable. In this regard, the post is typically provided with a radially enlarged barb to facilitate expansion of the cable jacket. The locking sleeve is then moved axially into the connector body to clamp the cable jacket against the post barb providing both cable retention and a water-tight seal around the cable jacket. The connector can then be attached to an external device by tightening the internally threaded nut to an externally threaded terminal or port of the external device.
The design objective of coaxial cables is to carry the electromagnetic field between the inner and outer conductor, while providing protection from external signal ingress, which may cause interference with the signal being transmitted. However, as community television (CATV) systems have become more sophisticated in carrying many more channels of analog and digital information, the problems of interference caused by the ingress of radio frequency (RF) signals have grown.
The conductive foil surrounding the center dielectric of newer coaxial cable designs include a layer of aluminum laminated on a layer of a polyester (PET) film (Mylar) tape. The foil is wrapped around the center dielectric with the Mylar layer making contact with the dielectric and with the aluminum layer forming the outer surface of the foil. Conventionally, the electrical signals will travel through the cable on the outer surface of the aluminum layer of the foil due to a phenomenon known in the field as the skin effect.
To shield the electrical signals traveling along the outer surface of the foil from RF interference, conventional coaxial cables typically include a conductive shield surrounding the foil. However, because the conductive shield surrounding the foil typically has a braided construction to provide flexibility to the cable, the electrical signals travelling on the outer surface of the foil are vulnerable to interference from RF energies due to the gaps in the shield resulting from the braided construction.
Some coaxial cable designs address this issue by providing an additional conductive foil layer to improve shielding. However, additional layers of foil also contribute to the cost of the cable. Moreover, while these newer conductive foil designs improve RF shielding to some extent, the present conventional coaxial cable connector interface designs do not provide reliable means to receive the energy from the foil layer.
Accordingly, it would be desirable to provide a coaxial cable connector that will provide improved RFI shielding. It would be further desirable to provide a coaxial cable connector with an improved RF interface that will maintain the signal propagating function of the cable throughout the coupling interface for full shielding benefits.